In the iOS 10.0 release notes, there are two mentions of RAW images:

The new AVCapturePhotoOutput class provides a unified pipeline for all photography workflows, enabling more sophisticated control and monitoring of the entire capture process and including support for new features such as Live Photos and RAW format capture. You should transition to AVCapturePhotoOutput instead of AVCaptureStillImageOutput, which is deprecated in iOS 10.

and

Core Image

The Core Image framework (CoreImage.framework) includes several enhancements.

RAW image file support is now available on iOS devices that use the A8 or A9 CPU. Core Image can decode RAW images produced by several third-party cameras as well as images produced by the iSight camera of supported iOS devices ... To process RAW images, use filterWithImageData:options: or filterWithImageURL:options: to create a CIFilter object, adjust RAW processing options with the keys listed in RAW Image Options, and read the processed image from the filter’s outputImage property.

So, it sounds as if both the built-in app and 3rd-party apps will have RAW access, but that support is limited by the CPU generation of the device (e.g., only iPhone 6 and later iPhones).